Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor having one or more rotor blades. The rotor blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, but not always, rotationally coupled to the rotor through the gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Such configurations may also include power converters that are used to convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency.
Renewable energy power systems, such as the wind turbine described above, typically includes a power converter with a regulated DC link controlled by a converter controller. More specifically, wind driven doubly-fed induction generator (DFIG) systems or full power conversion systems, typically include a power converter with an AC-DC-AC topology. For many wind turbines, the operating space, and hence value to the customer, is limited by maximum voltages for one or more wind turbine components, e.g. the DC link and the generator rotor, inherent to DFIG systems. Further, grid operating practices and failures may lead to increased or decreased voltages on the generator stator, which reflect onto the generator rotor and the DC link. In order to mitigate such voltage transients, the converter controller must either shift the rotor and stator power factor away from customer demanded set points or increase the rotor converter modulation index leading to higher harmonics observed by the customer. Such limitations tend to be more significant for DFIG generators that operate at a high rated slip (RPM) or for generators that are experiencing an over-speed condition.
In an effort to mitigate the aforementioned issues, various wind turbine control technologies have been implemented that utilize a voltage regulator to compare grid voltage to a threshold voltage value. The control system then commands a step change in the voltage regulator to maintain a specific margin to mitigate grid disturbances. Further systems have utilized larger converters or dynamic brakes to control voltage levels for over-speed and power-for-power factor demand limitations. Many of the systems described above, however, may require additional cost and/or complexity.
Thus, the present disclosure is directed to an improved system and method that addresses the aforementioned issues. More specifically, the present disclosure is directed to a system and method for optimizing wind turbine operation via a voltage regulator that is configured to maximize the margin-to-voltage thresholds of various wind turbine components.